Process for the peoduction of aluminium-plated zinc sheet



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NoDrawingl No. 680,386, In Germanylleeember 8, 1982 3 Claims. (Chit-189) All metals possess special physical and chemical properties by which they are distinguished from -each-other and this applies to aluminium and zinc and to metal sheets prepared therefrom.

The characteristic qualities of aluminium and aluminium sheet or plate are light weight, a clean white color, resistance to oxidation, the ease with which they may be mechanically worked as in rolling, drawing, prwsing and stamping; resistance to many acids; low degree of solidity as comdisagreeable appearance. 7 This oxidation of the surface, however, leads to a'resistance to a still deeper oxidation by air, moisture, and water in general. Further characteristics are brittleness in the cold state; easy workability in the heated condition, good solderability with white solder;

autogenous and electrical weldability; low degree ofsolidity compared with metals of higher melting point, ailinity for most of the acids, and want of. amnity for alkalies.

Fromthe above comparison of the two metals it is obvious that advantages in one of them are or may be in use disadvantages in the-other.

For the purpose of altering and improving the characteristics of aluminium and zinc the formation of an alloy of the two metals has been tried,

but these efforts have not met with complete succcss. Efforts have also been made in this direction by welding a sheet of one of the metals upon a sheet of the other, in such a manner as to obtain a one-sided or two-sided sheet, for example a zinc core with an aluminium coating,,or an aluminium core with zinc coatings. In this way the properties of the aluminium and zinc should balance each other; principally, the, combination sheet.

should be easier to work. It has been found that in general the plated sheet has a more resistant character and may be worked more advantageously than a non-plated sheet in rolling, stamping and soldering. From the chemical point of 'view a sheet as prepared, whether the core is zinc and the plating or covering of aluminium, or the reverse, presents the properties of the. outside coating, whether thatis aluminium or zinc. By

plating one metal upon the other, therefore, each side presentsits own properties according to the The present inventiomarises from recognition of the iact that the properties of zinc are greatly enhanced, especially for production in large quantities of aluminium-plated sheets, if an alloy is prepared 98-99% by weightof zinc and 2-1% being employed for the plating process with aluminium coatings or coverings.-

Systematic researches and experiments have shown that in these conditions not only are the properties of the zinc and aluminium improved, but also new and quite surprising properties show themselves in the plated productions. Zinc plates with the stated low aluminium contents of 1-2% give on being plated with aluminium a product that showsin particular greater strength or firmness and ductility or elongation as compared with products where ordinary zinc is plated with aluminium. In no other metal is it to be observed that increase of the ductility or elongation figure is inproportion to thehardness oi the sheet.

A further advantage of the invention is that sheet waste which is now useless for the purpose can be used up, being added to. the alloy composi tion, Obviously, also old material may be similarly used and added for the production of the new alloy.

As a surprising further advantage of the new alloy it is to be noted that this zinc-aluminium alloy is much more resistant to chemical action. For that reason it can be used for hygienic purposes in which'ordinary zinc would not be suitable. A one-sided plating of the zinc-alloy sheet with aluminium improves the electrical properties, and such sheets may be employed in the production of dry batteries in the known container form. Liberation or zinc through electrolysis is prolonged and equalized so that the battery has a longer eifective life. Further, the container for a can be easily and simply made, from a sheet ted on one side, by means of stamping. This. with ordinary zinc which cannot be stamped, is not powble.

After heating of the new sheets between 100 and 200 C. an intensive diffusion o; the metals occurs. At glowingheat the zincialloylof the. one

the ordinary sheet-steel which may be worked easily and formed into articles of all kinds whilst the finished articles may be tempered and hardened in known manner by water or oil. No other sheet metal but zinc-aluminium and steel exhibit these important properties. v e

As zihc and aluminium have about the same co-emcient' of expansion under heat, no separationofthesheetscanevertakeplace as aresult of temperature diiierences, an advantage which I no sheet-metal plated with another metal has so l 00 by weight of aluminium, zinc plates so prepared far e. no: a the sheet affected by electrical action, as the electrical properties of zinc and aluminium are favorable in this respect. The durable connection of the components of a sheet plated as described is not, therefore, endangeredin any direction.

A zinc sheet plated on both sides-with aluminium is waterproof and withstands sulphuric acidcontaining smoke gases, carbonic acid gas and soot, whilst, as is known, pure zinc does not. Again, with a sheet plated on one side only with aluminium, the zinc surface withstands alkalies, which an aluminium sheet does not.

A zinc sheet plated on both sides with the aluminium possesses, as pure aluminium sheet, great light and heat radiating properties and is, therefore, heat insulating, again a property not possessed by ordinary zinc sheet.

' the other the property of 'beingweldable and solderable, this because zinc is easily welded electrically and the aluminium coating is no hindrance. This is also the case in soldering, as the soldering iron easily burns away the aluminium and the zinc thus exposed naturally allows of soldering being effected.

Finally, the plated aluminium-zinc sheet exhibits extreme hardness in spite oftits great ductility. For instance, with a Brinell hardness of 50-65 the ductility or elongation figure is -20.

With the zinc-aluminium alloy according to the invention it is also possible to produce plated foil of greatthinnessto 0.003 mm.-by rolling, as the material possesses suflicient strength which is not the case with pure aluminium foil.

The production of the sheets is effected by rolling together heated zinc alloyed with 1-2% of aluminium at a somewhat higher temperature. The temperature figures for the different sheets will depend upon the thickness of the materials; it varies between 180 and 450 C.

By suitable composition or alloying of the aluminium component further new advantages are obtained. Especially may beindioated an aluminium alloy with silver and other precious metals as, for example, set forth in the British patent specification No. 354,202. These alloys are more resistant to corrosion than pure aluminium; they are not tarnished by the air and they have a silver-white sheen which aluminium itself does not exhibit to the same degree. Aluminium coatings on aluminium-alloyed zinc-sheets according to this invention have the same properties as set forth in the specification referred to, higher resistance to corrosion and silver-white appearance. The properties of the plated goods produced according to this invention are shortly summarised as follows:

(1') Increased strength-and ductility of the plated sheets and v (a) S ft qual ty Strength -25 Ductility (elongation) -65 Brinell hardness 40-50 (b) Hard quality Strength"; 25-32 Ductility (elongation) 10-20 Brinell hardness -65 (2) Great resistance of the aluminium zincalloy as ground material against chemical action and better hygienic properties as compared with usual zinc.

(3) Great resistance of the zinc sheet plated on both sides with aluminium against atmospheric influences, as also against sulphuric acidcontaining smoke gases, carbonic acid gas, soot, and so on.

(4) Absolute resistance of zinc sheets plated on one side only with aluminium to alkalies on the zinc side. (5) Great resistance and longer efiectiveness of zinc sheet plated with aluminium on one side to electrolytic attack when using the plated goods in the construction of electrical dry batteries.

('6) Favorable electrolytic suitability of the plated goods components and therefore distinct durability of the union of both such components.

(7) Security of the plated goods against unequal expansion of the sheets by thermic effects,

due to the almost equal co-eiiicients of both ance of the plated materials especially in the case of articles manufactured from a softer material whereby the difiusion process through the original aluminium-zinc alloy is shortened and the sheet made to show similar properties to steel sheet, that is to. say, it,can be tempered and hardened.

(10) Possibility of the plated goods being -1ike, as set forth in the British patent specification No. 354,202, the attainment of a better silverwhite sheen upon the goods.

I claim:

1. The method of increasing the ductility, hardness and diifusing tendency of metal. sheets and bands composed of layers welded together by pressure and comprising at least one layer of an alloy consisting chiefly of zinc and at least one layer consisting chiefly of aluminium, said method comprising using for the layer of zinc an alloy containing at least 98% and at the highest 99% of zinc, the rest being aluminium.

2. The method of increasing the ductility, hardness and diffusing capacity of metal sheets and bands composed of united layers comprising at least one'layer of an alloy consisting chiefly of aluminium, and at least one layer consisting chiefly of zinc, said method comprising using for. the layer of zinc an alloy containing at least 98% and at the highest 99% of zinc, the rest being aluminium, welding this layer together with the aluminium layer in heated state by pressure, cooling down the thus obtained compound sheet or band at ordinary temperature, and hardening it without subjecting it to pressure by re-heating it to a temperature in the range of from 100 to 200 C. so as to obtain dlfiusion of the metals.

3. The method of increasing the ductility, hardalso produced by rolling and being heated to a temperature not below 180 C. and not above 450 C., welding said layers together by rolling mill pressure at a temperature lying below the temperature of said layer of aluminium, cooling the thus plated alloy plate to atmospheric pressure, and transforming it between polished rollers of a, rolling mill into a foil of not less than 0.003 mm. thickness.

FRANZ JORDAN. 

